Flexible couplings are useful in various applications where there is a need to connect a drive source, such as a motor, to a peripheral device, in which the components might be subject to initial misalignment or dynamically misaligned in use due to the nature of the components.
Flexible couplings are also used to reduce the transmission of stress and vibration between two or more connected components. For example, in oil well drilling and pumping there are severe shocks and vibrations that are detrimental to the drilling and pumping equipment. Drilling assemblies used in the oil and gas industry to retrieve resources buried within earth formations typically include a drilling string connected to a drill bit. The drilling string includes interconnected pipe segments with the drill bit positioned at a distal end thereof. As the drill bit cuts through the earth, vibrations, usually at high frequencies, occur and are transmitted along the drilling string. These high frequency vibrations may cause fatigue, deterioration, and finally failure of the components of the drilling assembly. In addition, drill string sections may comprise highly sensitive electronic devices. The electronics must be isolated from the same high frequency vibrations, as well as other applied stresses. Furthermore, the electronic devices must be isolated from torsional loads that occur during acceleration or deceleration of the section carrying the electronics.
In progressive cavity devices, oil well drilling fluid is pumped through a progressive cavity motor that drives the bit. In oil production, particularly for heavy crude, an electric submersible motor drives the progressive cavity pump to pump oil out of the ground. The progressive cavity device can be used as a motor or pump depending on whether it is driven by fluid (motor) or by being turned by an electric motor (pump). U.S. Pat. No. 3,323,326 (Vertson) discloses a metal elastomer helix coupled to a metal elastomer spline that is connected to the drill string to dampen vibrations. The helix consists of a metal male/female thread separated by an elastomer. The spline section consists of a metal female spline separated by an elastomer. U.S. Pat. No. 5,447,472 (Ide) shows two metal/elastomer helixes connected by a shaft that acts like a universal type coupling to compensate for misalignments between the drive motor and drive shaft. U.S. Pat. No. 5,833,541 (Turner/Ide) shows one end of the helix shown in U.S. Pat. No. 5,447,472 to dampen vibrations for instrumentation and a one directional tapered metal/elastomer helix. U.S. Pat. No. 6,808,455 (Sobrenko/Miller) shows a metal/elastomer spline for torsional shock absorption. The elastomer is unbonded and tapered longitudinally to provide a non-linear stiffness. U.S. Pat. No. 6,916,248 (Burgess) shows the single helix of U.S. Pat. No. 5,833,541 but with a double tapered thread to prevent separation.
As drilling motors become more powerful, there is a need to provide a higher torque coupling.